Thermoset polymeric composition from poly-oxazoline and alkenyl phosphonic acid

ABSTRACT

A process for the preparation of a thermoset polymer having good adhesive properties comprising reacting a compound containing a plurality of oxazoline groups with an alkenyl phosphonic acid at a temperature of from about room temperature to about 300° C. is described.

This invention relates to a process for the rapid copolymerization of acompound containing a plurality of oxazoline groups with an alkenylphosphonic acid either alone or in the presence of other reactivematerials and to the novel thermoset products which result from saidcopolymerization.

The synthesis of thermoplastic and thermoset polymers containing poly(ether-amide) groups by reaction of bis-oxazolines with bis- andpolyphenolics is described in U.S. Pat. No. 4,430,491.

The copolymerization of bis-oxazolines with alkenyl phosphonic acidseither alone or in the presence of reactive materials such aspolyphenolics, polycarboxylic acids and polyepoxides has not previouslybeen disclosed in the prior art.

The copolymerization of bis-oxazolines with reactive materials such aspolyphenolics, polycarboxylic acids and polyepoxides to givethermoplastic and thermoset polymers in the absence of any catalyst isusually very slow. I have discovered that the copolymerization ofbis-oxazolines with alkenyl phosphonic acids is a very rapid reactionand that high temperature resistant thermoset polymers can be preparedat a rapid rate without catalysts when bis-oxazolines are copolymerizedwith alkenyl phosphonic acids either alone or with other reactivematerials such as polyphenolics. The resulting polymers show goodadhesion properties toward metal substrates and may also be used inreaction injection molding (RIM), thermoset, and composite applications.

The oxazolines useful in the practice of this invention include avariety of such compounds having at least two 2-oxazoline groups permolecule. The applicable polyfunctional oxazolines are devoid of otherfunctional groups capable of reacting in any manner with either anoxazoline group or an aromatic hydroxyl group. From the standpoint ofpotential commercial availability the oxazolines derived from thepolycarboxylic acids are preferred. Particularly exemplary of suchpolyacids are the aromatic acids; e.g., isophthalic acid, terephthalicacid and trimesic acid. The polyfunctional oxazoline compounds can beconveniently prepared by the reaction of the corresponding esters ofsaid polyacids and ethanolamines.

Representative polyfunctional oxazoline compounds useful in the practiceof this invention include 4,4',5,5'-tetrahydro-2,2'-bisoxazole, a2,2'-(alkanediyl) bis[4,5-dihydrooxazole], e.g., 2,2'-(1,4-butanediyl)bis [4,5-dihydrooxazole]; a 2,2'-(arylene) bis [4,5-dihydrooxazole],e.g. 2,2'-(1,4-phenylene) bis [4,5-dihydrooxazole],2,2'-(1,5-naphthalenyl) bis [4,5-dihydrooxazole] and2,2'-(1,8-anthracenyl) bis [4,5-dihydrooxazole]; a sulfonyl, oxy, thioor alkylene bis 2-(arylene) [4,5-dihydrooxazole], e.g., sulfonyl bis2-(1,4-phenylene) [4,5-dihydrooxazole], oxy bis 2-(1,4-phenylene)[4,5-dihydrooxazole], thio bis 2-(1,4-phenylene) [4,5-dihydrooxazole]and methylene bis 2-(1,4-phenylene) [4,5-dihydrooxazole]; a2,2',2"-(arylene) tris [4,5-dihydrooxazole], e.g., 2,2',2"-(1,3,5-phenylene) tris [4,5-dihydrooxazole]; a poly[2-(alkenyl)4,5-hydrooxazole], e.g., poly[2-(2 -propenyl)4,5-dihydrooxazole], and the like.

Polyphenolic compounds useful in the present invention include compoundshaving at least two aromatic hydroxy groups per molecule andparticularly the bisphenols, the various benezene and fused aromaticring diols and triols, e.g., 1,4-benzene diol (hydroquinone),1,3benzenediol (resorcinol), 1,4-naphthalene diol and 1,3,5-benzenetriol; the biphenyl diols, e.g., [1,1'-biphenyl]-2,2'-diol; the alkyleneand cycloalkylene bisphenols, e.g., 2,2'-methylene bisphenol,4,4'-(1-methylethylidene) bisphenol (Besphenol-A),4,4'-(phenylmethylene) bisphenol, 4,4'-(cyclohexanediyl) bisphenol,4,4'-(1,2-diethyl-1,2-ethenediyl) bisphenol, and3,4-bis(4-hydroxyphenyl)-2,4-hexadiene; the arylene bisphenols, e.g.,4,4'-phenylene bisphenol; the oxy, thio and sulfonyl bis phenols, e.g.,2,3-oxybisphenol, 4,4'-thiobisphenol and 2,2'-sulfonyl bisphenol; thebis (hydroxyaryl) alkanones, e.g., bis (4-hydroxyphenyl) methanone,1,5-dihydroxy-9.10-anthracenedione and 4-[bis(4-hydroxyphenyl)methylene]-2,5-cyclohexadiene-1-one; the various benzamide and benzoatederivatives, e.g., 2-hydroxy-N-(4-hydroxyphenyl) benzamide,4-hydroxy-4-hydroxyphenyl benzoate, 2-methyl-2-[(4-hydroxybenzoyl) oxymethyl]-1,3-propanediyl-4-hydroxybenzoate, bis (4-hydroxybenzoate)-1,2-ethandiyl; 2-(4 -hydroxy benzoate) ethyl ether, and bis(4-hydroxy benzamide)-1,4-benzenediyl and the like.

In addition to the phenolic compounds noted above, a variety ofoligomers containing a plurality of phenolic residues constitute animportant class of materials for the reaction with the oxazolines andalkenyl phosphonic acids in this invention. These phenolic compoundsinclude the base or acid caralyzed phenol-formaldehyde condensationproducts such as the novalaks, the resoles and phenolic resinscharacterized in having the benzylic ether linkages prepared by metalion catalysts such as disclosed in U.S. Pat. No. 3,485,797. Othersuitable polyphenol oligomers include the addition polymers andcopolymers of a vinyl substituted phenol, e.g., 4-ethenylphenol.

The alkenyl phosphonic acids useful in the present invention includethose having the formula I ##STR1## wherein R, R' and R" independentlyrepresent hydrogen, an alkyl group having from 1 to 10 carbon atoms, anaryl group having from 6 to 12 carbon atoms or an alkaryl group havingfrom 7 to 15 carbon atoms.

In the process of this invention the alkenyl phosphonic acid serves as amultifunctional molecule. The hydroxyl groups of the phosphonic acid arebelieved to react with the oxazoline rings to give ring opening productscontaining phosphonate and amide groups. The alkenyl groups may beeither homopolymerized or copolymerized with other unsaturated moleculesby using a free radical or cationic catalyst. The copolymerizablemonomers with the alkenyl gorup may include unsaturated hydrocarbons(e.g. styrene, acrylic acid and methacrylic acid and derivatives, vinylesters such as vinyl acetate, acrylonitrile, methacrylonitrile,acrylamide, methacrylamide and the like). In such reactions, the alkenylphosphonic acid may also behave as an oxazoline ring openinghomopolymerization catalyst, thus the copolymerization ofbis-2-oxazoline with alkenyl phosphonic acid may also be carried out inthe presence of other reactive materials such as polyphenolics,polycarboxylic acids, polyepoxides, polylthiols, polyamides and imides,mixtures thereof and the like. In these polymerization reactions, theamounts of bis-oxazoline to alkenyl phosphonic acid can be in the rangeof 99/1 to 50/50 by weight. The process of this invention may be carriedout at a temperature in the range of from about room temperature toabout 300° C.

In the copolymerization reactions involving bis-oxazoline/reactivematerial such as polyphenolics/alkenyl phosphonic acid, the ratio ofbis-oxazoline to reactive material may be in the amounts (based onequivalents) in the range of 1:1 to 10:1 and the alkenyl phosphonic acidmay be used in from 1 to 30% by weight based on the weight of the totalreactants. The polymers obtained in the reactions of bis-oxazoline withreactive material such as polyphenolics and alkenyl phosphonic acid showhigh glass transition temperatures and thermal stabilities. The polymersof this invention show good flame retardant properties and they alsohave good adhesion toward metals such as steel and aluminum.

This invention is further illustrated in the following representativeexamples.

EXAMPLE 1

Isophthaloyl bis-oxazoline (4.5 g) and isopropenyl phosphonic acid (2 g)were mixed and heated at 165 degrees C. A clear solution formed within20 seconds which gelled within one minute to give a thermoset polymer.This polymer was postcured at about 170 degrees C. for one hour. Thepolymer was found to be insoluble in solvents such as acetone,tetrahydrofuran (THF) and dimethylformamide (DMF). The T_(g) (glasstransition temperature) of the polymer as determined by DSC(differential scanning calorimetry) was found to be 154 degrees C. and10% weight loss by thermal gravimetry analysis (TGA) was found to occurat 318 degrees C.

EXAMPLE 2

Isophthaloyl bis-oxazoline (4.3 g) and resorcinol (1.6 g) were mixed and0.5 g of isopropenyl phosphonic acid was added and the mixture washeated at 165 degrees C. A clear solution formed within 20 seconds whichgelled within one minute to give a solid polymer. This polymer waspostcured at 170 degrees C. for one hour. The product was found to beinsoluble in common organic solvents such as acetone, THF, and DMF. TheT_(g) by DSC was found to be 165.2 degrees C. and the 10% weight loss byTGA occurred at 328 degrees C.

EXAMPLE 3

This is a comparative example to demonstrate the formation of athermoplastic polymer at a slow rate in the reaction of a bis-oxazolinewith resorcinol and is outside the scope of this invention. Isophthaloylbisoxazoline (10.0 g) and resorcinol (3.5 g) were mixed and heated at165 to 158 degrees C. No gelation occurred within five minutes and onlya thermoplastic material formed on heating for about 1 hour. The heatingwas continued for 31/2 hours to give a polymeric material which wasfound to be soluble in solvents such as DMF and showed a melting pointof 75 degrees C. indicating it to be thermoplastic.

EXAMPLE 4

A mixture of 4.52 g of isophthaloyl bis-oxazoline, also called2,2'-(1,3-phenylene) bis [4,5-dihydrooxazole]3.5 g of a polyphenoliccompound (Alnovol 320 from American Hoescht, a novalak type resinresulting from the phenol formaldehyde reaction), and 0.6 g ofisopropenyl phosphonic acid was heated at 170 degrees C. with stirring.A clear solution formed within 25 seconds which gelled within one minuteto give a thermoset polymer. The polymer, after postcuring at 170degrees C. for one hour, was found to have a T_(g) (DSC) of 198 degreesC. and a 10% weight loss by TGA at 335 degrees C.

EXAMPLE 5

A mixture of 4.3 g of isophthaloyl bis-oxazoline, 4.2 g of Alnovol, 2 gof liquid diglycidyl ether of Bisphenol-A and 0.4 g of isopropenylphosphonic acid was heated at 165 degrees C. A clear solution occurredwithin 20 seconds of heating and the solution gelled in approximatelytwo minutes to give a pale yellow solid polymer. The polymer was foundto have a T_(g) (DSC) of 177 degrees C. and a 10% weight loss by TGAoccurred at 334 degrees C.

EXAMPLE 6

A mixture of 5.1 g of isophthaloyl bis-oxazoline, 2.5 g of adipic acidand 0.5 g of isopropenyl phosphonic acid containing 1% t-butylperbenzoate, was heated at 170 degrees C. Gelation occurred within 1.5minutes to give a thermoset polymer. The polymer was postcured at 200degrees C. for one hour. The product was found to have a T_(g) (DSC) of78 degrees C. and a 10% weight loss by TGA occurred at 313 degrees C.

EXAMPLE 7

This comparative example which is outside the scope of this inventiondemonstrates that a thermoplastic polymer is formed when a bis-oxazolineand adipic acid are copolymerized. A mixture of 5 g of isophthaloylbis-oxazoline and 2.6 g of adipic acid were heated at 170 degrees C. andno gelation occurred within five minutes. The mixture gradually becameviscous upon continued heating for two hours and the solid polymer wasfound to be soluble in DMF at room temperature.

EXAMPLE 8

A mixture of phthaloyl bis-oxazoline, 2.8 g of Alnovol and 0.5 g ofisopropenyl phosphonic acid containing 1% of 5-butyl perbenzoate washeated at 170 degrees C. The mixture gelled within two minutes and thepolymer was postcured at 200 degrees C. for one hour. The polymer wasfound to have a T_(g) (DSC) of 191 degrees C. and the thermaldecomposition (10% weight loss by TGA) was at 345 degrees C.

EXAMPLE 9

A mixture of 5.3 g of phthaloyl bis-oxazoline, 2.5 g of adipic acid and0.6 g of isopropenyl phosphonic acid containing 1% 5-butyl perbenzoatewas heated at 160 degrees C. for 30 seconds to give a clear solution.This liquid was applied between (1) two 1"×4" aluminum panels and (2)two cold rolled steel panels covering one square inch overlap area andthe bonds were cured at 170 degrees C. for 15 minutes. The lap shearstrength on an Instron instrument showed strengths of 1550 psi(aluminum) and 1230 psi (steel).

EXAMPLE 10

A mixture of 4.0 g of phthaloyl bis-oxazoline, 2.8 g of Alnovol and 10.6g of isopropenyl phosphonic acid containing 1% of t-butyl perbenzoatewas heated at 165 degrees C. for 30 seconds to give a clear liquid. Thisliquid was applied between two 1"×4" panels of (1) cold rolled steel and(2) aluminum, covering one square inch overlap area in each case. Thebonds were cured by heating at 170 degrees C. for 15 minutes and theresulting structures showed lap shear strengths of 950 psi (steel) and1470 psi (aluminum).

EXAMPLE 11

A mixture of 4.5 g of phthaloyl bis-oxazoline, 4.0 g of Alvonol, 2.4 gof diglycidyl ether of Bisphenol-A and 0.6 g of isopropenyl phosphonicacid was prepared. This mixture was heated at 165 degrees C. for 30seconds to give a clear liquid and the liquid was applied between two1"×4" panels of (1) aluminum and (2) cold rolled steel, covering onesquare inch overlap area. The bonds were cured at 165 degrees C. for 15minutes and tested at room temperature for lap shear strength. The lapshear strength for aluminum was 1430 psi and for cold rolled steel was1380 psi.

I claim:
 1. A process for preparing a thermoset polymer comprisingreacting a compound containing a plurality of oxazoline groups with analkenyl phosphonic acid at a temperature in the range of from about roomtemperature to about 300° C.
 2. The process of claim 1 wherein thecompound containing a plurality of oxazoline groups is one containing atleast two 2-oxazole groups per molecule.
 3. The process of claim 2wherein the alkenyl phosphonic acid is one having the formula ##STR2##wherein R, R', and R" independently represent hydrogen, an alkyl grouphaving from 1 to 10 carbon atoms, an aryl group having from 6 to 12carbon atoms or an alkaryl group having from 7 to 15 carbon atoms. 4.The process of claim 3 wherein the amounts of compound containing aplurality of oxazoline groups to alkenyl phosphonic acid is in the rangeof from 99/1 to 50/50 by weight.
 5. The process of claim 4 wherein thecompound containing a plurality of oxazoline groups is isophthaloylbis-oxazoline.
 6. The thermoset polymer prepared by the process of claim1.